HELP! 727 driveshaft problem

O.K. Put a 340 and a 727 In my 69 valiant. Motor runs perfect. I go to put the driveshaft In and It wont fit. I ordered the 727 yoke from summit. Still wont fit. And yes the tranny is a 727. and it is new. Question is "Did the 727 have different splines on the output shaft on early models, say, pre 67?. Any help would be awesome! Thanks